Re: hash join and nested loop join in an oltp query

On 05/04/2004 02:43:13 PM, ryan.gaffuri_at_cox.net wrote: >
> what types of cases make hash joins superior to nested loops? I see them alot in batch processing when I need > to join most of the rows, but I am see them now when I return a small subset of rows.

Well, if you have to use full table scan to retrieve rows from one of the tables, there is a strong probability that hash join will be faster then the nested loop approach. Of course, there is a slight problem with the word OLTP, because full table scans are not allowed in OLTP queries.

> has anyone experienced this?

Probably.

-- 
Mladen Gogala
Oracle DBA



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